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Indicator: Air Emissions

Summary

In 2001–02, 62 substances listed on the National Pollutant Inventory were known to be emitted to air, land or water in the ACT. The most significant source of emissions in the ACT is motor vehicles, although light industry, domestic activities (such as using wood-heaters, leakage from gas appliances, sewage and waste disposal), landfill and agricultural activities also contribute. Because motor vehicles make such a significant contribution, the regulations for emissions from vehicles have been tightened over recent years, and will be tightened even further in future. The bushfires of January 2003 caused a marked spike in emissions into the atmosphere.

What the results tell us about the ACT

More than 62 pollutants are known to have been emitted to air, land and water in the ACT in 2001–02, down from 67 the preceding year. Not all of these substances are necessarily significant to the state of the environment, but it is useful to maintain a database of them.

Without heavy industry or power stations burning coal or oil in the ACT region, the majority of atmospheric emissions come from motor vehicles. Burning solid fuels, especially wood for heating, is also an important source, as are bushfires, when they occur. There are also emissions from leaking gas appliances, landfill, waste disposal, agricultural activities and petrol stations.

Transport emissions

The National Pollutant Inventory (NPI) estimates that motor vehicles are the largest single source of atmospheric emissions in the ACT, and accounted for about 24% of all emissions to air in 2001–02. According to the New South Wales Environmental Protection Agency, motor vehicles in New South Wales account for 70% of NOx emissions, 52% of volatile organic compound emissions and 23% of particulate emissions in urban areas. It is likely that these percentages are similar for these pollutants in the Canberra urban area.

Motor vehicles

Motor vehicle emissions are affected by various factors, including the type of vehicle and its age, the fuel used, how well maintained the vehicle is, and how and where it is driven. Better roads and less ‘stop–start’ driving reduces emissions, so Canberra’s good and relatively uncongested road system probably helps reduce emissions.

In the 12-month period ending 31 October 2002, the average annual distance travelled by each ACT motor vehicle was 15,100 kilometres, slightly above the national vehicle average of 15,000 kilometres. The total annual distance travelled by registered motor vehicles in the ACT was estimated to be 3108 million kilometres in 2002. This is an increase on the figure for 2001 (3048 million) but a noticeable decrease on the 2000 figure (3228 million). Passenger vehicles accounted for the overwhelming majority of kilometres travelled – 2635 million kilometres, or 84.8% of all travel.

The quantity of fuel used per 100 kilometres travelled has decreased during this time, as vehicles have become more efficient. This is an important point when considering air emissions.

The number of registered vehicles in the ACT continues to increase with population. In 2002 there were 206,444 motor vehicles in the ACT, the majority (177,436) being passenger vehicles. It is reasonable to assume that total distance travelled, and total vehicle emissions, will therefore also increase. However, improvements in vehicle technology, stricter standards for emissions in new vehicles, and smaller vehicles mitigate this effect. Total vehicle emissions will not necessarily increase in line with total kilometres travelled.

The average age of private motor vehicles in the ACT is about 10 years. Most of these vehicles would have been built in compliance with the 1986 legislation on emissions (ADR 37/00). Cars made in Australia from 1997 onwards must comply with stricter controls, set out in ADR 37/01. From 2003, the even stricter ADR 79/00 applies, implementing the ‘Euro 2’ design and emission rules. In future, the ‘Euro 3’ and ‘Euro 4’ rules will apply (see Table 1 in the downloadable pdf version).

Aircraft

In 2000–01, total passenger aircraft movements at Canberra airport increased by 26% to 51,867 movements. The exhaust vapours of aircraft flying lower than about 1000 metres are usually taken as contributors to the lower airshed. The emissions of aircraft flying higher than 1000 metres are widely dispersed, and not considered in local emissions levels. Aircraft emissions are similar to those of motor vehicles, as listed below:

Industrial emissions

Industrial facilities are required to report emissions if they use more than a set level of one or more substances on the NPI reporting list, or consume more than a specified amount of fuel or electric power. Although there are few industrial facilities in Canberra, 23 facilities in the ACT are required to report to the NPI. Almost all of these emit very small amounts of listed pollutants. During the reporting period, the main change in industrial facilities was at the Totalcare incinerator at Mitchell, which stopped operating in November 2000.

Architectural surface coatings

Apart from the wide range of pollutants in motor vehicle exhaust, Canberra air also receives emissions from other sources. The principal diffuse source is classified by the NPI as architectural surface coatings, which includes paints, primers, lacquers and the solvents and thinners used in their application.

The main emissions from architectural surface coatings are volatile organic compounds which evaporate as the coating dries. Solvent-based coatings contain from 30–70% Volatile organic compounds by weight, while water-based coatings contain only about 6%. When architectural surface coatings are applied using spray guns, especially on exterior surfaces, this may also lead to emissions of particulate matter.

Emissions from bushfires

Burning vegetation, such as during the January 2003 bushfires, is a source of many air pollutants, including monitored ones such as particulates and carbon monoxide, and unmonitored but potentially dangerous compounds such as benzene and other volatile organic carbon compounds. Results from monitoring in January 2003 show a spike in the concentration of particulates, carbon monoxide, nitrogen dioxide and ozone in Canberra’s air. People close to the fires would have been exposed to high loads of additional pollutants from the burning synthetic materials found in houses and vehicles. As well as causing immediate respiratory distress and eye damage, some of these emitted substances may also be long-term carcinogens.

Emissions from wood-burning heaters

Solid fuel burning in fires for home heating is another important source of air emissions in Canberra. Particulate concentrations in Canberra are usually highest in winter because of wood heaters, coupled with valley conditions and the presence of atmospheric inversion layers that can trap pollutants overnight.

Point sources of atmospheric emissions

There are four point sources of atmospheric emissions in the ACT that have been granted environmental authorisations and are required to report their air emissions to Environment ACT. They are:

The atmospheric pollutants and volumes emitted are known for all of these facilities, other than the crematorium. It is assumed that, if the crematorium is operated correctly, emissions are relatively small and non-toxic. However, the United Kingdom’s National Atmospheric Emissions Inventory estimated that in 1998, crematoria accounted for 11% of the United Kingdom’s total atmospheric mercury emissions. Mercury emissions at crematoria are mainly from dental fillings in corpses. The United Kingdom study suggested that an average of 0.9 grams of mercury vapour is released per cremation. Other heavy metals, which accumulate in the body during life, may also be emitted by crematoria.

Environmental authorisations

Since 1 July 1998, various environmental authorisations of potential relevance to air emissions have been issued. These have all been standard authorisations, granted under section 49 of the Environment Protection Act 1997(see Table 2 in the downloadable pdf version).

Environmental protection agreements

In the same period, a number of environmental protection agreements of potential relevance to air emissions were made (see Table 3 in the downloadable pdf version).

Air toxics

Many of the NPI-listed pollutants are classified as ‘air toxics’ or 'hazardous air pollutants'. These can be gases, aerosols or particulates present in the air in low concentrations that are sufficiently toxic to be a hazard to human, plant or animal life. It is unclear what health impacts, if any, they may have at these levels. Often there are insufficient data about this and some effects may not become evident for decades or may not necessarily be directly attributable to exposure. Air toxics include volatile and semi-volatile organic compounds (toluene, xylene, carbon tetrachloride), polycyclic aromatic hydrocarbons (benzene and derivatives), heavy metals (cadmium, mercury) and aldehydes (formaldehyde).

There is growing international recognition of the potential health risks associated with exposure to air toxics and of the need for action to minimise these risks. There is evidence that some air toxics are carcinogenic, or may be associated with birth defects, genetic damage, immunodeficiency and other long-term problems. They can also have more immediate, short-term effects in higher concentrations. Air toxics come from a wide range of sources. The exposure of the Australian population to these substances is dependent on individual lifestyle and places of work and residence. Common sources in Canberra are motor vehicle exhaust, service stations, woodburning heaters, tobacco smoke, spray-painting and dry cleaning. Many substances evaporate easily, and are therefore easily inhaled. The eventual fate of many is to be deposited onto water, soil or vegetation and, over time, this can lead to an accumulation of the pollutants and/or modification by biological and physical processes.

Because air toxics disperse quickly, concentrations vary widely, and the effects on individuals also vary, determining their health effects is difficult. A draft National Environmental Protection Measure for air toxics is being considered. The compounds to be covered are benzene, toluene, xylene, formaldehyde and polycyclic aromatic hydrocarbons. All documents associated with development of the measure are available on the web at >.

About the data

Currently, levels of some pollutants are compared against the standards set by the National Environment Protection Measures (or NEPMs). In particular, levels of sulphur dioxide, carbon monoxide, nitrogen oxides, particles, lead and ozone are compared to the Ambient Air Quality NEPM in the Outdoor air quality indicator. Emissions linked to the greenhouse effect, depletion of upper atmosphere ozone, or indoor air quality are dealt with elsewhere.

Substances can be categorised as significant either by virtue of the quantity emitted or because of their environmental or human health implications. A substance may be highly toxic, in which case emission of even small quantities is significant. Conversely, relatively large quantities of less harmful substances can be emitted to air with little environmental or health impact. Thus, the receiving capacity of the environment is a major factor in whether a substance has a deleterious effect. The capacity includes the ability of natural biological or physical processes to degrade, disperse or alter pollutants into less harmful (occasionally more harmful) forms. Little is known about the receiving capacity in the atmosphere for most emitted substances. In addition, the receiving capacity can be altered by factors such as local topography, season, weather or elevation.

The most significant pollutants in vehicle exhaust are carbon monoxide, oxides of nitrogen, particulates, and a group of compounds collectively called volatile organic compounds. Volatile organic compounds can react with other substances in the environment to form ozone, and some of them are known, or suspected, carcinogens. All these substances are potentially damaging to health, although the effects depend on dosage over time, route of administration, and differences between individuals. For some of these substances, uncertainty remains about what constitutes a safe level for public health.

Known pollutants are listed by the National Pollutant Inventory (NPI). The data held are based on information supplied by governments and industrial and commercial facilities. This information may not necessarily concern absolute quantities emitted. Rather it may be data for usage rates, from which emissions can be estimated. NPI data for the ACT is currently available for 1999–2000 and 2001–02.

The NPI holds emission data reported by industrial facilities, and aggregated emission data collected by participating jurisdictions. Industrial facilities are required to report emissions to the NPI if they use substances on the NPI reporting list, or consume more than a specified amount of fuel or electric power, or emit more than a certain amount of nitrogen or phosphorus to water. Aggregated data include smaller facilities that are not required to report, and mobile and non-industrial sources, such as transport, domestic activities, and for water catchments and landuse type.

The techniques used to estimate emissions in the NPI have been variously approved by federal, state and territory environment agencies but it is important to note that the accuracy of these estimates is likely to vary according to the technique used. For the aggregated emissions data in particular, comparative analysis of the data may be misleading, because jurisdictions may have used different approved estimation techniques. Industrial facilities estimate emissions using a technique described in an appropriate NPI handbook, or else otherwise approved.

Environmental Impact of the New Australian Hybrid Cars 2000, PC Manins. Appeared in: Proceedings of the 15th International Clean Air and Environment Conference, Sydney , NSW, Clean Air Society of Australia and New Zealand. pp. 117–22.